944 Cold idle behaviour...

[1.2gees]

I'm wondering, if 944s are supposed to idle any higher when cold, compared to hot?

My engine runs a bit rough when first started, after about 30 seconds, it smooths out noticably, and at once.

I've posted this before, and many times I got the reply that they're supposed to idle around 900 regardless. Well, why would the car have an aux air regulator if it won't idle any higher? Guess I'm gonna have to check mine, hope I take care of this before my spring break is over.
Ahmet

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It's all the driver...

[CJFusco]

My car always idles at about 900, but it is noticably rougher when cold. I just watch the oil pressure meter until it drops below 4, then I figure it is warm enough to drive.

[andrew4266]

My car always idled rough when cold. yesterday i spent the afternoon cleaning the intake manifold and throttle body. they had a considerable amount of gunk built up on them. it did make a big difference. it idles alot smoother and has restored some power. i have the 16v engine so it was a bit tougher to get everything apart but well worth it.

[redNeckarsulm2]

you've got a single wire o2 sensor, right?
Maybe the car runs rough until it warms up enough to operate correctly..

[Ehab]

Ahmet,
I've already posted my situation (I have the same car as you do, without any mods), The car seems to run rich for about 30 seconds (the MPG meter is around 20 at idle), I guess the DME does this until the O2 sensor warms up, in addition to the oil and other things that need to warm up. After this 'timed' period, my car's rpm drops to 700 or so (and MPG meter goes back to about 50) and almost stalls when the weather is cold enough, and I think that is because MY AAV is not functioning to let in the extra air in to stabilize the rpm. In YOUR case, the rpm stays at around 900, which might imply that your AAV is working fine.

I would really like to know how the AAV works. I know that it is supposed to let in more air to un-choke the car when cold. But the Haynes manual says that when the car is warm, the AAV is CLOSED, but if you pinch the hose, the rpm should drop!!! WHY, if the AAV is closed, then shouldn't that hose have no effect on rpm when warm?????

I would appreciate any knowledge/thoughts ...
Thanks.


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Lock Stock '84 944 and two smokin' tires ...

[1.2gees]

The idle is supposed to drop, if you pinch the hose, with the engine cold (when the aux valve is OPEN).

What I'm curious about is though, howcome the idle doesn't go UP when the car's cold, if the aux valve is open, and the car's running rich??? Just a cold engine thing, I know they're not supposed to run as efficient when cold but...
Ahmet

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It's all the driver...

[porsche1987_944s]

my car idles at 2000 until it warms and then drops to around 900-1100 once it warms.

[asidrave]

my car stays at the same idle on cold start and hot at about 900. check the cold start valve and/or the o2 sensor. well im not sure how you go about checking the cold start valve, a new one from porsche goes for about $35

[Ehab]

I would love to change my aux air valve, or at least clean it!!! But the right allen screw is so damn hard to get to with the standard 6mm allen key, the damn intake manifold is in the way ...
any tips?


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Lock Stock '84 944 and two smokin' tires ...

[AMCPorsche924Powerhaus!]

Well with the 924s its the exact same thing.
Some people say yes, it is supposed to fast idle, and some say it is always suppposed to be the same rpm regardless.
Mine fast idles.

I think the reason it isn't supposed to fast idle, is because you have an overly rich mixture when cold...have you ever adjusted your fuel mixture to a little too rich?
The idle moves down. So this extra richness actaully takes the idle down, taking the fast idle away (aux air).
When you richen your mix the idle moves down and you say "but what about my aux air valve, it ads extra air", well the aux air is just like holding the pedal down a little, it adds air and fuel, not just air.
The name aux air is confusing because you think it just means air is added.
So the AUX air is just like pressing on the accelerator, it's not as if it is just adding auxillary air, it is adding fuel and air in proportion.
So, you have a rich mix with the cold start fuel added (warm up reg on '24s, i don't know about '44s) causing your idle to drop from 900, but then aux air valve pulls up the idle from that drop back to 900.

Think of it as setting your mixture too rich, and pressing the pedal down to keep the car from not stalling...

Have you ever richened the mixture and not touched the idle speed? the car will stall....

As for why some of us (including me) have the fast idle? I think its because something isn't working...on my car the warm up reg adds extra fuel, probably isn't working, so just the aux air valve revs up the motor without the rich mix, since rich would take it down if it WAS working.


[This message has been edited by AMCPorsche924Powerhaus! (edited 04-12-2001).]

[AMCPorsche924Powerhaus!]

Ahmet when your car first gets started and is stumbly, does pressing down on the accelerator a tad make it better? If so its the aux air that is the culprit, and your extra fuel adding is fine...
If it stalls when you press on the accelerator a bit, or shows no response, well then its probably the aux air AND the richenign thing not working, which is more unlikely then just one not working.
Or if it stalls when you press on accelerator it could be they are both worn out and/or dirty, so they aren't working to spec.

[1.2gees]

Hmm, my car runs/idles fine, and does have power (but the throttle is that tiny bit touchy when cold)...

Yes, the car runs considerably smoother, if it were to idle about 70rpm faster. A slight touch on gas makes it quite smooth (but the engine turns faster too, up to a bit shy of 1k, instead of around 900). Interesting, if I had time I'd look at it, but today I'll be playing with the control arms, having two tires on, getting the state, and track tech inspection done, so probably won't have time until monday, which is my last day off.
Ahmet

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It's all the driver...

[AMCPorsche924Powerhaus!]

maybe the tach is slightly off too and the aux air valve is just not opening enough during the thirty seconds...
On my car the tach reads high, at about 950RPM it is actaully 900 on an accurate external tach